Method and Apparatus of Delivering Protocol Data Units for a User Equipment in a Wireless Communications System

ABSTRACT

A method of delivering protocol data units (PDUs) for a user equipment in a wireless communications system includes receiving a reordering PDU from a protocol entity. The reordering PDU has a PDU sequence. A first PDU of the PDU sequence is a segment of a PDU having a segmented side at the front, and a last PDU of the PDU sequence is a segment of a PDU having a segmented side at the end. The first PDU and a previously stored PDU segment are discarded when the reordering PDU and the previously stored PDU segment are not consecutive. All PDUs other than the first PDU and the last PDU in the reordering PDU are delivered to an upper layer entity of the protocol entity and the last PDU is stored.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60,916,546, filed on May 7, 2007 and entitled “Method and Apparatus forallocating HARQ configuration and concatenation and delivery of MACPDUs”, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for deliveringprotocol data units (PDUs) in a user equipment of a wirelesscommunications system, and more particularly to a method and apparatusfor improving concatenation and delivery of MAC-ehs PDUs in a userequipment of a wireless communications system.

2. Description of the Prior Art

The third generation (3G) mobile telecommunications system has adopted aWideband Code Division Multiple Access (WCDMA) wireless air interfaceaccess method for a cellular network. WCDMA provides high frequencyspectrum utilization, universal coverage, and high quality, high-speedmultimedia data transmission. The WCDMA method also meets all kinds ofQoS requirements simultaneously, providing diverse, flexible, two-waytransmission services and better communication quality to reducetransmission interruption rates.

In the prior art, lengths of all Protocol Data Units (PDUs) outputtedfrom a Radio Link Control (RLC) layer are the same. However, thisdecreases bandwidth utility rate and data processing efficiency,especially for high data rate applications, such as High Speed DownlinkPackage Access (HSDPA) and High Speed Uplink Package Access (HSUPA) inthe 3G mobile telecommunications system. Thus, targeting high data rateapplications, the 3rd Generation Partnership Project (3GPP) makes somemodifications for RLC and Media Access Control (MAC) layers, whichprimarily includes adopting flexible RLC PDU sizes and providing PDUsegmentation/reassembly in the MAC layer, to enhance bandwidth utilityrate and data processing efficiency, thereby making high data rateenabled by physical layer features such as Multi-input Multi-output(MIMO) and high order modulations possible.

In such a situation, the 3GPP newly introduces a MAC-ehs protocol entityin the MAC layer, which allows the support of flexible RLC PDU sizes aswell as MAC segmentation/reassembly. Furthermore, unlike MAC-ehs forHSDPA, MAC-ehs allows multiplexing of data from several priority queueswithin one transmission time interval (TTI) of 2 ms. Detailed operationsof the MAC-ehs entity can be found in the MAC protocol specificationformulated by the 3GPP, and are not narrated herein.

Please refer to FIG. 1, which illustrates a schematic diagram of aMAC-ehs PDU. The MAC-ehs PDU consists of a plurality of reordering PDUsR_PDU_(n) and a corresponding MAC-ehs header. Each reordering PDUconsists of at least one consecutive MAC-ehs Serving Data Unit (SDUs) orsegments of MAC-ehs SDUs belonging to the same priority queue, orreordering queue. A MAC-ehs SDU, i.e. an upper layer PDU, is either aMAC-c PDU or a MAC-d PDU. For each reordering PDU, the MAC-ehs headercarries a Logical channel identifier (LCH-ID) field LCH-ID_(n), a Lengthfield L_(n), a Transmission Sequence Number (TSN) field TSN_(n), aSegmentation Indication (SI) field SI_(n), and a header extension fieldF_(n). The LCH-ID field LCH-ID_(n) indicates a priority queue for eachreordering PDU, wherein the mapping between the logic channel and thepriority/reordering queue is provided by upper layers. The Length fieldL_(n) indicates data length of each reordering PDU. The TSN fieldTSN_(n) indicates a TSN of each reordering PDU for reordering purpose.The SI field SI_(n) indicates whether MAC-ehs SDUs included in eachreordering PDU are segmented and segmentation type of the reordering PDUfor reassembly. The header extension field F_(n) then indicates whetherthere exists a next reordering PDU in the following.

Thus, when a MAC-ehs PDU is received by the UE, each reordering PDU isfirstly assigned to a corresponding reordering queue for reorderingaccording to the LCH-ID field LCH-ID_(n) and the TSN field TSN_(n). Ineach reordering queue, if the latest received reordering PDU isdetermined to be consecutive to a previously stored segment of a MAC-ehsSDU, the reordering PDU shall be further concatenated with thepreviously stored segment of the MAC-ehs SDU according to the SI fieldSI_(n), so that a complete MAC-ehs SDU can be delivered to upper layers.

According to the above MAC protocol, the SI field is indicated by twobits, and thus includes four segmentation types:

1) Type ‘00’: indicates that a first MAC-ehs SDU and a last MAC-ehs SDUin a reordering PDU are not segmented.

2) Type ‘01’: indicates that a first MAC-ehs SDU in a reordering PDU isa front-end segmented upper layer PDU; and, if there are more than oneMAC-ehs SDUs in the reordering PDU, a last MAC-ehs SDU in the reorderingPDU is not segmented.

3) Type ‘10’: indicates that a last MAC-ehs SDU in a reordering PDU is aback-end segmented upper layer PDU; and, if there are more than oneMAC-ehs SDUs in the reordering PDU, a first MAC-ehs SDU in thereordering PDU is not segmented.

4) Type ‘11’: indicates that a first MAC-ehs SDU in a reordering PDU isa front-end segmented upper layer PDU; and a last MAC-ehs SDU in thereordering PDU is a back-end segmented upper layer PDU.

In the prior art, when a reordering PDU with the SI field=‘11’ isreceived, the UE may firstly determine whether the reordering PDU isconsecutive to a previously stored PDU segment according to a TSN or theSI field of the reordering PDU. If the reordering PDU is consecutive tothe previously stored PDU segment, a first MAC-ehs SDU in the reorderingPDU shall be concatenated with the previously stored PDU segment. Ifthere is only one MAC-ehs SDU in the reordering PDU, which must be asegment of an upper layer PDU being segmented at both ends according tothe above MAC protocol, the only one MAC-ehs SDU of the reordering PDUafter being concatenated with the previously stored PDU segment is stillnot a complete upper layer PDU, such that the concatenated PDU shall bestored for being concatenated with a later-received reordering PDU.

On the other hand, if there is more than one MAC-ehs SDU in thereordering PDU, which means there exist at least a front-end segmentedupper layer PDU and a back-end segmented upper layer PDU, the firstMAC-ehs SDU in the reordering PDU after being concatenated with thepreviously stored PDU segment then forms a complete MAC-ehs SDU. In thiscase, the concatenated MAC-ehs SDU and other complete MAC-ehs SDUs inthe reordering PDU shall be delivered to upper layers, such as tocorresponding logic channels through a demultiplexing entity. Finally,the last MAC-ehs SDU of the reordering PDU is stored for beingconcatenated with a later-received reordering PDU.

Conversely, if the reordering PDU is not consecutive to the previouslystored PDU segment, the first MAC-ehs SDU in the reordering PDU and thepreviously stored PDU segment shall be discarded, so as to preventincorrect concatenation of later-received reordering PDUs with thepreviously stored PDU segment.

However, when the reordering PDU is not consecutive to the previouslystored PDU segment, operations such as delivering other complete MAC-ehsSDUs in the reordering PDU to the upper layers and storing the lastMAC-ehs SDU of the reordering PDU are not performed. In some situations,such as when there more than one MAC-ehs SDU exists in the reorderingPDU, a data error or delay may occur in the UE, since other completeMAC-ehs SDUs in the reordering PDU may be incorrectly discarded.

SUMMARY OF THE INVENTION

It is therefore an objective of the present invention to provide amethod and apparatus for delivering protocol data units in a userequipment of a wireless communications system.

According to the present invention, a method for delivering protocoldata units, named PDUs hereinafter, in a user equipment of a wirelesscommunications system is disclosed. The method includes steps ofreceiving a reordering PDU from a protocol entity, wherein thereordering PDU comprises a PDU sequence, a first PDU of the PDU sequenceis a front-end segmented PDU, and a last PDU of the PDU sequence is aback-end segmented PDU; discarding the first PDU and a previously storedPDU segment when the reordering PDU and the previously stored PDUsegment are not consecutive; and delivering all PDUs other than thefirst PDU and the last PDU in the reordering PDU to an upper layerprotocol entity of the protocol entity and storing the last PDU.

According to the present invention, a communications device used in awireless communications system for delivering protocol data units, namedPDUs hereinafter, is further disclosed. The communications deviceincludes a control circuit for realizing functions of the communicationsdevice; a processor installed in the control circuit, for executing aprogram code to command the control circuit; and a memory installed inthe control circuit and coupled to the processor for storing the programcode. The program code includes steps of receiving a reordering PDU froma protocol entity, wherein the reordering PDU comprises a PDU sequence,a first PDU of the PDU sequence is a front-end segmented PDU, and a lastPDU of the PDU sequence is a back-end segmented PDU; discarding thefirst PDU and a previously stored PDU segment when the reordering PDUand the previously stored PDU segment are not consecutive; anddelivering all PDUs other than the first PDU and the last PDU in thereordering PDU to an upper layer protocol entity of the protocol entityand storing the last PDU.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic diagram of a MAC-ehs PDU.

FIG. 2 is a functional block diagram of a communications device.

FIG. 3 is a schematic diagram of the program code in FIG. 2.

FIG. 4 is a schematic diagram of a process according to an embodiment ofthe present invention.

DETAILED DESCRIPTION

Please refer to FIG. 2, which is a functional block diagram of acommunications device 100. For the sake of brevity, FIG. 2 only shows aninput device 102, an output device 104, a control circuit 106, a centralprocessing unit (CPU) 108, a memory 110, a program code 112, and atransceiver 114 of the communications device 100. In the communicationsdevice 100, the control circuit 106 executes the program code 112 in thememory 110 through the CPU 108, thereby controlling an operation of thecommunications device 100. The communications device 100 can receivesignals input by a user through the input device 102, such as akeyboard, and can output images and sounds through the output device104, such as a monitor or speakers. The transceiver 114 is used toreceive and transmit wireless signals, delivering received signals tothe control circuit 106, and outputting signals generated by the controlcircuit 106 wirelessly. From a perspective of a communications protocolframework, the transceiver 114 can be seen as a portion of Layer 1, andthe control circuit 106 can be utilized to realize functions of Layer 2and Layer 3.

Please further refer to FIG. 3, which is a schematic diagram of theprogram code 112 in FIG. 2. The program code 112 comprises anapplication program layer 200, a layer 3 interface 202, a layer 2interface 206, and a layer 1 interface 218. When transmitting signals,the layer 3 interface 202 submits Service Data Units (SDUs) 208 to thelayer 2 interface 206 and the layer 2 interface 206 stores the SDUs 208in a buffer 212. Then, the layer 2 interface 206 generates a pluralityof PDUs 214 according to the SDUs 208 stored in the buffer 212 andoutputs the PDUs 214 generated to a destination through the layer 1interface 218. Conversely, when receiving a radio signal, the radiosignal is received through the layer 1 interface 218 and the layer 1interface 218 outputs PDUs 214 to the layer 2 interface 206. The layer 2interface 206 restores the PDUs 214 to SDUs 208 and stores the SDUs 208in the buffer 212. Finally, the layer 2 interface 206 transmits the SDUs208 stored in the buffer 212 to the layer 3 interface 202. Preferably,the communications device 100 is applied in an Evolved High Speed PacketAccess (Evolved HSPA) system, such that the layer 2 interface 206 can bea MAC-ehs interface utilized for handling MAC-ehs PDUs.

When a MAC-ehs PDU is received by the communications device 100, eachreordering PDU in the MAC-ehs PDU is firstly assigned to a correspondingreordering queue for reordering and reassembly. In this case, theembodiment of the present invention provides a PDU delivering programcode 220 in the program code 112 utilized for correctly delivering PDUsto upper layers. Please refer to FIG. 4, which illustrates a schematicdiagram of a process 30 according to an embodiment of the presentinvention. The process 30 is utilized for delivering PDUs in a userequipment of a wireless communications system, and can be compiled intothe PDU delivering program code 220. The process 30 includes thefollowing steps:

Step 300: Start.

Step 302: Receive a reordering PDU from a protocol entity, wherein thereordering PDU comprises a PDU sequence, a first PDU of the PDU sequenceis a front-end segmented PDU, and a last PDU of the PDU sequence is aback-end segmented PDU.

Step 304: Discard the first PDU and a previously stored PDU segment whenthe reordering PDU and the previously stored PDU segment are notconsecutive.

Step 306: Deliver all PDUs other than the first PDU and the last PDU inthe reordering PDU to an upper layer protocol entity of the protocolentity and store the last PDU.

Step 308: End.

According to the process 30, a reordering PDU is firstly received in areordering queue. The reordering PDU is carried in a MAC-ehs PDU andincludes a PDU sequence. The first PDU of the PDU sequence is afront-end segmented PDU while a last PDU of the PDU sequence is aback-end segmented PDU. If the reordering PDU is determined not to beconsecutive to the previously stored PDU segment, the first PDU and thepreviously stored PDU segment shall be discarded to prevent incorrectconcatenation of later-received reordering PDUs with the previouslystored PDU segment. Finally, all PDUs other than the first PDU and thelast PDU in the reordering PDU shall be delivered to upper layers, andthe last PDU of the reordering PDU shall be stored in the embodiment ofthe present invention.

In other words, for a reordering PDU received by the UE, when a firstPDU is a front-end segmented PDU and a last PDU is a back-end segmentedPDU, i.e. a Segmentation Indication (SI) header field corresponding tothe reordering PDU is ‘11’, if the reordering PDU is not consecutive tothe previously stored PDU segment, not only the first PDU of thereordering PDU and the previously stored PDU segment are discarded, butoperations of delivering other complete upper layer PDUs in thereordering PDU to upper layers, such as delivering to correspondinglogic channels through a demultiplexing entity, and storing the last PDUof the reordering PDU are also performed in the embodiment of thepresent invention. Therefore, concatenation and delivery of MAC-ehs PDUscan then be correctly executed by the communications device 100, so asto improve situations of data error and delay occurred in the prior art.

Please note that, in Step 304, the situation in which the reordering PDUand the previously stored PDU segment are not consecutive furtherincludes no PDU segment being previously stored, so that at this time,only the first PDU of the reordering PDU needs to be discarded in theembodiment of the present invention.

In addition, when there is only one MAC-ehs SDU in the reordering PDUreceived by the UE, i.e. the only one MAC-ehs SDU must be a segment ofan upper layer PDU being segmented at both ends, the reordering PDU canstill be correctly handled through the process 30 of the presentinvention, which also belongs to the scope of the present invention.Certainly, the process 30 can further include steps of: determiningwhether the first PDU and the last PDU in the reordering PDU aresegmented and segmentation types thereof according to the SI fieldcorresponding to the reordering PDU; and determining whether thereordering PDU is consecutive to the previously stored PDU segmentaccording to a Transmission Sequence Number (TSN) header field or the SIfield corresponding to the reordering PDU, which are well-known by thoseskilled in the art, and are not narrated herein.

Therefore, for the reordering PDU received by the UE, if the first PDUis a front-end segmented PDU, the last PDU is a back-end segmented PDU,and the reordering PDU is not consecutive to the previously stored PDUsegment, the embodiment of the present invention further delivers allcomplete PDUs in the reordering PDU to the upper layers and stores thelast PDU of the reordering PDU, except for discarding the first PDU ofthe reordering PDU and the previously stored PDU segment, so as toimprove situations of data error and delay occurring in the prior art.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

1. A method for delivering protocol data units, named PDUs hereinafter,in a user equipment of a wireless communications system, the methodcomprising: receiving a reordering PDU from a protocol entity, whereinthe reordering PDU comprises a PDU sequence, a first PDU of the PDUsequence is a front-end segmented PDU, and a last PDU of the PDUsequence is a back-end segmented PDU; discarding the first PDU and apreviously stored PDU segment when the reordering PDU and the previouslystored PDU segment are not consecutive; and delivering all PDUs otherthan the first PDU and the last PDU in the reordering PDU to an upperlayer protocol entity of the protocol entity and storing the last PDU.2. The method of claim 1, wherein discarding the first PDU and thepreviously stored PDU segment when the reordering PDU and the previouslystored PDU segment are not consecutive comprises discarding the firstPDU when no PDU segment is previously stored.
 3. The method of claim 1,wherein the previously stored PDU segment is a back-end segmented PDU.4. The method of claim 1 further comprising: determining whether thefirst PDU and the last PDU in the reordering PDU are segmented andsegmentation types thereof according to a segmentation indication headerfield corresponding to the reordering PDU.
 5. The method of claim 1,wherein the reordering PDU is carried in a MAC-ehs PDU.
 6. The method ofclaim 1 further comprising: determining whether the reordering PDU isconsecutive with the previously stored PDU segment according to atransmission sequence number header field or a segmentation indicationheader field corresponding to the reordering PDU.
 7. The method of claim1, wherein the PDU sequence comprises a plurality of consecutive PDUs,and the plurality of consecutive PDUs are MAC-ehs serving data units,named MAC-ehs SDUs, comprising MAC-d PDUs or MAC-c PDUs.
 8. The methodof claim 1, wherein the wireless communications system is an EvolvedHigh Speed Packet Access system.
 9. A communications device used in awireless communications system for delivering protocol data units, namedPDUs hereinafter, the communications device comprising: a controlcircuit for realizing functions of the communications device; a centralprocessing unit coupled to the control circuit for executing a programcode to operate the control circuit; and a memory coupled to the centralprocessing unit for storing the program code; wherein the program codecomprises: receiving a reordering PDU from a protocol entity, whereinthe reordering PDU comprises a PDU sequence, a first PDU of the PDUsequence is a front-end segmented PDU, and a last PDU of the PDUsequence is a back-end segmented PDU; discarding the first PDU and apreviously stored PDU segment when the reordering PDU and the previouslystored PDU segment are not consecutive; and delivering all PDUs otherthan the first PDU and the last PDU in the reordering PDU to an upperlayer protocol entity of the protocol entity and storing the last PDU.10. The communications device of claim 9, wherein discarding the firstPDU and the previously stored PDU segment when the reordering PDU andthe previously stored PDU segment are not consecutive comprisesdiscarding the first PDU when no PDU segment is previously stored. 11.The communications device of claim 9, wherein the previously stored PDUsegment is a back-end segmented PDU.
 12. The communications device ofclaim 9, wherein the program code further comprises: determining whetherthe first PDU and the last PDU in the reordering PDU are segmented andsegmentation types thereof according to a segmentation indication headerfield corresponding to the reordering PDU.
 13. The communications deviceof claim 9, wherein the reordering PDU is carried in a MAC-ehs PDU. 14.The communications device of claim 8, wherein the program code furthercomprises: determining whether the reordering PDU is consecutive withthe previously stored PDU segment according to a transmission sequencenumber header field or a segmentation indication header fieldcorresponding to the reordering PDU.
 15. The communications device ofclaim 9, wherein the PDU sequence comprises a plurality of consecutivePDUs, wherein the plurality of consecutive PDUs are MAC-ehs serving dataunits, named MAC-ehs SDUs, comprising MAC-d PDUs or MAC-c PDUs.
 16. Thecommunications device of claim 9, wherein the wireless communicationssystem is an Evolved High Speed Packet Access system.